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	$191.71	4.524%	$200.383	$200.38	$200.40	$200.40
Purchase #2	$64.25	4.209%	$66.9543	$66.95	$66.95	$67.00
Purchase #3	$114.61	11.591%	$127.8944	$127.89	$127.90	$127.90
Purchase #4	$159.69	9.160%	$174.3176	$174.32	$174.30	$174.30
Purchase #5	$229.55	10.295%	$253.1822	$253.18	$253.20	$253.20
Purchase #6	$194.55	12.555%	$218.9758	$218.98	$219.00	$219.00
Purchase #7	$123.75	4.691%	$129.5551	$129.56	$129.55	$129.60
7 purchase totals =	$1,078.11		$1,171.2624	$1,171.26	$1,171.30	$1,171.40