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	$210.33	9.141%	$229.5563	$229.56	$229.55	$229.60
Purchase #2	$148.84	4.217%	$155.1166	$155.12	$155.10	$155.10
Purchase #3	$142.49	7.769%	$153.56	$153.56	$153.55	$153.60
Purchase #4	$203.64	9.640%	$223.2709	$223.27	$223.25	$223.30
Purchase #5	$99.60	5.512%	$105.09	$105.09	$105.10	$105.10
Purchase #6	$51.97	6.550%	$55.374	$55.37	$55.35	$55.40
Purchase #7	$108.63	11.131%	$120.7216	$120.72	$120.70	$120.70
7 purchase totals =	$965.50		$1,042.6894	$1,042.69	$1,042.60	$1,042.80