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	$201.86	4.520%	$210.9841	$210.98	$211.00	$211.00
Purchase #2	$147.81	12.454%	$166.2183	$166.22	$166.20	$166.20
Purchase #3	$58.73	11.303%	$65.3683	$65.37	$65.35	$65.40
Purchase #4	$52.83	11.737%	$59.0307	$59.03	$59.05	$59.00
Purchase #5	$245.67	10.473%	$271.399	$271.40	$271.40	$271.40
Purchase #6	$81.77	10.664%	$90.49	$90.49	$90.50	$90.50
Purchase #7	$202.84	4.838%	$212.6534	$212.65	$212.65	$212.70
7 purchase totals =	$991.51		$1,076.1438	$1,076.14	$1,076.15	$1,076.20