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	$147.27	5.690%	$155.6497	$155.65	$155.65	$155.60
Purchase #2	$198.56	12.746%	$223.8685	$223.87	$223.85	$223.90
Purchase #3	$48.29	8.607%	$52.4463	$52.45	$52.45	$52.40
Purchase #4	$31.49	6.318%	$33.4795	$33.48	$33.50	$33.50
Purchase #5	$216.92	6.280%	$230.5426	$230.54	$230.55	$230.50
Purchase #6	$234.28	3.435%	$242.3275	$242.33	$242.35	$242.30
Purchase #7	$192.44	12.187%	$215.8927	$215.89	$215.90	$215.90
7 purchase totals =	$1,069.25		$1,154.2068	$1,154.21	$1,154.25	$1,154.10