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	$77.60	11.228%	$86.3129	$86.31	$86.30	$86.30
Purchase #2	$166.57	12.210%	$186.9082	$186.91	$186.90	$186.90
Purchase #3	$94.41	7.765%	$101.7409	$101.74	$101.75	$101.70
Purchase #4	$88.31	7.302%	$94.7584	$94.76	$94.75	$94.80
Purchase #5	$80.95	11.854%	$90.5458	$90.55	$90.55	$90.50
Purchase #6	$185.86	13.318%	$210.6128	$210.61	$210.60	$210.60
Purchase #7	$147.62	6.112%	$156.6425	$156.64	$156.65	$156.60
7 purchase totals =	$841.32		$927.5215	$927.52	$927.50	$927.40