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	$177.68	4.428%	$185.5477	$185.55	$185.55	$185.50
Purchase #2	$89.34	11.538%	$99.648	$99.65	$99.65	$99.60
Purchase #3	$68.33	6.787%	$72.9676	$72.97	$72.95	$73.00
Purchase #4	$109.98	13.180%	$124.4754	$124.48	$124.50	$124.50
Purchase #5	$243.68	8.330%	$263.9785	$263.98	$264.00	$264.00
Purchase #6	$62.31	8.819%	$67.8051	$67.81	$67.80	$67.80
Purchase #7	$242.35	7.747%	$261.1249	$261.12	$261.10	$261.10
7 purchase totals =	$993.67		$1,075.5472	$1,075.56	$1,075.55	$1,075.50