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	$154.40	11.133%	$171.5894	$171.59	$171.60	$171.60
Purchase #2	$107.91	6.608%	$115.0407	$115.04	$115.05	$115.00
Purchase #3	$197.56	9.204%	$215.7434	$215.74	$215.75	$215.70
Purchase #4	$82.69	9.585%	$90.6158	$90.62	$90.60	$90.60
Purchase #5	$179.57	3.237%	$185.3827	$185.38	$185.40	$185.40
Purchase #6	$209.28	9.791%	$229.7706	$229.77	$229.75	$229.80
Purchase #7	$150.53	13.531%	$170.8982	$170.90	$170.90	$170.90
7 purchase totals =	$1,081.94		$1,179.0408	$1,179.04	$1,179.05	$1,179.00