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	$146.52	5.435%	$154.4834	$154.48	$154.50	$154.50
Purchase #2	$196.54	7.229%	$210.7479	$210.75	$210.75	$210.70
Purchase #3	$245.80	11.336%	$273.6639	$273.66	$273.65	$273.70
Purchase #4	$53.41	5.596%	$56.3988	$56.40	$56.40	$56.40
Purchase #5	$28.89	9.364%	$31.5953	$31.60	$31.60	$31.60
Purchase #6	$92.99	13.807%	$105.8291	$105.83	$105.85	$105.80
Purchase #7	$247.65	9.478%	$271.1223	$271.12	$271.10	$271.10
7 purchase totals =	$1,011.80		$1,103.8407	$1,103.84	$1,103.85	$1,103.80