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	$174.71	4.326%	$182.268	$182.27	$182.25	$182.30
Purchase #2	$191.37	10.207%	$210.9031	$210.90	$210.90	$210.90
Purchase #3	$236.68	11.233%	$263.2663	$263.27	$263.25	$263.30
Purchase #4	$96.89	4.134%	$100.8954	$100.90	$100.90	$100.90
Purchase #5	$52.25	13.521%	$59.3147	$59.31	$59.30	$59.30
Purchase #6	$225.70	4.280%	$235.36	$235.36	$235.35	$235.40
Purchase #7	$128.69	7.339%	$138.1346	$138.13	$138.15	$138.10
7 purchase totals =	$1,106.29		$1,190.1421	$1,190.14	$1,190.10	$1,190.20