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	$223.37	12.430%	$251.1349	$251.13	$251.15	$251.10
Purchase #2	$94.26	5.717%	$99.6488	$99.65	$99.65	$99.60
Purchase #3	$76.73	12.490%	$86.3136	$86.31	$86.30	$86.30
Purchase #4	$238.38	7.113%	$255.336	$255.34	$255.35	$255.30
Purchase #5	$99.93	9.215%	$109.1385	$109.14	$109.15	$109.10
Purchase #6	$96.67	4.823%	$101.3324	$101.33	$101.35	$101.30
Purchase #7	$136.41	13.234%	$154.4625	$154.46	$154.45	$154.50
7 purchase totals =	$965.75		$1,057.3667	$1,057.36	$1,057.40	$1,057.20