Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$142.25	7.391%	$152.7637	$152.76	$152.75	$152.80
Purchase #2	$245.90	12.312%	$276.1752	$276.18	$276.20	$276.20
Purchase #3	$155.81	11.682%	$174.0117	$174.01	$174.00	$174.00
Purchase #4	$232.93	9.742%	$255.622	$255.62	$255.60	$255.60
Purchase #5	$113.27	8.669%	$123.0894	$123.09	$123.10	$123.10
Purchase #6	$209.89	4.279%	$218.8712	$218.87	$218.85	$218.90
Purchase #7	$195.25	4.257%	$203.5618	$203.56	$203.55	$203.60
7 purchase totals =	$1,295.30		$1,404.0950	$1,404.09	$1,404.05	$1,404.20