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	$104.33	5.292%	$109.8511	$109.85	$109.85	$109.90
Purchase #2	$108.55	5.604%	$114.6331	$114.63	$114.65	$114.60
Purchase #3	$132.28	12.830%	$149.2515	$149.25	$149.25	$149.30
Purchase #4	$247.50	12.618%	$278.7296	$278.73	$278.75	$278.70
Purchase #5	$58.36	10.764%	$64.6419	$64.64	$64.65	$64.60
Purchase #6	$204.35	11.688%	$228.2344	$228.23	$228.25	$228.20
Purchase #7	$147.45	11.408%	$164.2711	$164.27	$164.25	$164.30
7 purchase totals =	$1,002.82		$1,109.6127	$1,109.60	$1,109.65	$1,109.60