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	$175.75	10.483%	$194.1739	$194.17	$194.15	$194.20
Purchase #2	$156.83	9.280%	$171.3838	$171.38	$171.40	$171.40
Purchase #3	$71.85	4.550%	$75.1192	$75.12	$75.10	$75.10
Purchase #4	$105.26	3.579%	$109.0273	$109.03	$109.05	$109.00
Purchase #5	$33.48	4.399%	$34.9528	$34.95	$34.95	$35.00
Purchase #6	$54.49	8.456%	$59.0977	$59.10	$59.10	$59.10
Purchase #7	$154.83	11.663%	$172.8878	$172.89	$172.90	$172.90
7 purchase totals =	$752.49		$816.6425	$816.64	$816.65	$816.70